Physiology 206 Lecture 10 Outline of Last Lecture I. Cholinergic neuronsII. Somatic branch of nervous systemIII. Neurotoxins Outline of Current Lecture I. MuscleII. Thick filamentsIII. Thin filamentsIV. ContractionV. Types of contractionCurrent Lecture2/7/14- Muscle-3 categorieso Skeletal-voluntary, striated muscleo Smooth-involuntary, visceral, non-striatedo Cardiac-heart muscle- Voluntary muscles can be consciously controlled- Muscle cells are cylindricalo Muscle fiber = muscle cell- Myofibrils-long, cylindrical groups of proteinso Actin: thinner, known as thin filamentso Myosin: thicker, known as thick filamentso “acto-mysolin” fibers- Muscles generate tensions- Thin filaments: bundles of actin- Thick filaments: made up of myosin- Thin and thick filaments:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Regular, repeting arrayo Lengthwise along muscle- Cross bridges: molecular connections between thick and thin filaments near tipo Give muscle cell longitudinal rigidity- Muscle cells bound together to form a muscle- Sarcomere length: ~2 micormeters- Biological systems use ATP (made by mitochondria)- Motor neuron: o release Ach onto the motor endplateo Ach binds cholergenic receptors onto the endplateo Generates action potential in muscle- Sarcolemma is smooth covering that dips into cytoplasem (t-tubules)- Action potential propagated through entire plasmolemma and down into sarcolemmao Down into body of cell onto sarcoplasmic reticulum- Sarcoplasmic reticulumo Releases calcium into cytoplasmo Release of calcium causes contraction- Contractiono Sliding Filament Mechanism Myofibrils slide across each other- Ends of thin and thick filaments become closer- Shortens muscleo Isometric contraction Generate force without shortening Cells shorten but muscles don’to Isotonic contraction Can shorten without generating force Generate motion at constant force Movement of limbsLength-tensions DiagramsTensionLength - Passive Tensiono As you increase length, you increase tensionso Not active, no energy requiredo Elasticity: stretchability of musclesTensionI I I I I (electricity)Length- Tension will increase, reach a maximum, then decline- With the little tension, the ends of the thick and thin filaments are far apart- At maximum tension, the ends of thick and thin filaments are completely alignedActive
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